澳大利亚望远镜大面积巡天：ELAIS-S1和CDF-S的2.3 GHz观测
The Australia Telescope Large Area Survey: 2.3 GHz observations of ELAIS-S1 and CDF-S
摘要：
上下文澳大利亚望远镜大区域巡天（ATLAS）的目标是以欧洲大区域ISO巡天-南1（ELAIS-S1）场和钱德拉深场南（CDF-S）为中心，以1.4 GHz的高灵敏度（高达~10 \muJy）对7 deg 2区域进行成像，以研究恒星形成星系（SFG）和活动星系核（AGN）在广泛的宇宙时间范围内的演化。目标。我们在这里提出的辅助无线电观测频率为2.3 GHz的澳大利亚望远镜紧凑阵列（ATCA）。其主要目标是研究前所未有的大样本源的无线电频谱（在两个频率上观察到约2000个，检测到约600个）。方法.在本文中，我们提供了2.3 GHz的源目录的两个ATLAS字段，与300 \muJy的检测限。我们使用匹配的分辨率图像计算1.4 GHz和2.3 GHz之间的光谱指数，并研究我们的源样本的光谱指数的依赖性的各种属性。结果我们发现整个源样品具有0.74的中值光谱指数，与光学薄同步辐射的典型值0.7和由各个小组进行的其他光谱指数研究都很好地一致。关于无线电频谱指数作为源类型的指标，我们发现只有边际的相关性，使平坦或倒置的频谱源通常由活动星系核供电，因此得出结论，至少对于微弱的人口的频谱指数是不是一个强大的干扰。我们调查了光谱指数和红移之间的关系，我们的源样本，并没有发现这样的相关性。我们确实发现了红移和无线电与近红外通量比之间的显着相关性，使其成为高Z射电源的更强示踪剂。我们也没有发现任何证据的依赖性的无线电-红外相关光谱指数。
英文摘要：
Context. The Australia Telescope Large Area Survey (ATLAS) aims to image a 7 deg2 region centred on the European Large Area ISO Survey - South 1 (ELAIS-S1) field and the Chandra Deep Field South (CDF-S) at 1.4 GHz with high sensitivity (up to ~10 \muJy) to study the evolution of star-forming galaxies (SFGs) and Active Galactic Nuclei (AGN) over a wide range of cosmic time. Aims. We present here ancillary radio observations at a frequency of 2.3 GHz obtained with the Australia Telescope Compact Array (ATCA). The main goal of this is to study the radio spectra of an unprecedented large sample of sources (~2000 observed, ~600 detected in both frequencies). Methods. With this paper, we provide 2.3 GHz source catalogues for both ATLAS fields, with a detection limit of 300 \muJy. We compute spectral indices between 1.4 GHz and 2.3 GHz using matched resolution images and investigate various properties of our source sample in dependence of their spectral indices. Results. We find the entire source sample to have a median spectral index of 0.74, in good agreement with both the canonical value of 0.7 for optically thin synchrotron radiation and other spectral index studies conducted by various groups. Regarding the radio spectral index as indicator for source type, we find only marginal correlations so that flat or inverted spectrum sources are usually powered by AGN and hence conclude that at least for the faint population the spectral index is not a strong discriminator. We investigate relation between spectral index and redshift for our source sample and find no such correlation at all. We do find a significant correlation between redshift and radio to near-infrared flux ratio, making this a much stronger tracer of high-z radio sources. We also find no evidence for a dependence of the radio-IR correlation on spectral index.
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